I'm using Debian 8 with Openbox which comes with PulseAudio by default. And I cannot find a volume icon which works properly.
I try Volti (the volume becomes very low and sometimes doesn't work), Pavucontrol (doesn't have a volume icon) and try to compile pa-applet (I can't compile then! Many others have the same problem) and volctl (doesn't appear on the panel).
I didn't try volumeicon because in many forums people say that they don't work properly with PulseAudio, so I did not even try then.
I read about pulseaudio-ctl, but it hasn't a volume icon.